NEW BEDFORD — Maybe because it began life as a commercial fishing vessel, the big blue boat that cleared customs at the State Pier in New Bedford this week has attracted little attention on the waterfront.

But the 128-foot Ocearch, a former Bering Sea crabber, has bigger fish to fry these days. After a 52-day voyage from Cape Town in South Africa, the boat will spend the next month hunting for great white sharks in the waters off Cape Cod. And the sharks will live to tell the tale.

"These sharks are a 400-million-year-old secret. We don't know where they are breeding, feeding or giving birth," said expedition leader and vessel owner Chris Fischer. "What we do is provide the best scientists access to these sharks to gather information and help demystify the life of Jaws."

The Ocearch's crew includes experienced sportfishermen who travel the world's oceans to catch the sharks, which are then corralled in a specially designed research platform. The sharks are raised out of the water to be measured, bio-sampled, tagged and released by teams of local marine scientists, he said.

"Using Fischer's platform will give us a direct satellite linkup, and that's something we don't have," said Greg Skomal, a shark expert with the state's Division of Marine Fisheries. Blood samples taken from the captured sharks will also be measured to quantify the stress to the animal from its capture. Skomal said he will be happy if they succeed in tagging up to 10 white sharks.

Scientists from the University of Massachusetts and the New England Aquarium have also expressed interest in joining the project, which is being financed by Fischer, he said.

Tagging provides real-time tracking for up to five years, said Fischer, who founded and funded the nonprofit Ocearch by producing television shows about his work. His goal, he said, is to increase our knowledge of these animals to ensure that they have a future. "I believe all conservation decisions should be driven by data rather than emotion," he said.

Great white sharks are the great balance-keepers of the ocean, Fisher said, and they need greater protection.

While recent publicity surrounding local shark sightings — as well as a likely attack on a swimmer on the Cape — might lead people to believe shark numbers are increasing, the truth is shark populations worldwide are in wholesale decline, researchers have found.

During its two months in South Africa, Ocearch tagged and released 56 sharks, both great whites and ragged tooth sharks, according to the ship's captain and lead fisherman Jody Whitworth of Fort Lauderdale, Fla.

A satellite transmitter on the fin of a shark will transmit every time it comes out of the water, he said, tracking its movements. Transmitters were also implanted under the skin of the captured sharks, and their signals can be picked up by receivers on the shore when a shark is nearby, alerting beachgoers to their presence.

Bob Heuter, a senior scientist with the Mote Marine laboratory in Sarasota, Fla., will be joining Skomal on the local expedition. Working the waters off Chatham offers scientists a great opportunity to learn more about these animals, he said.

"The Ocearch people are experts in this," Heuter said. "I've worked with them before on studies with hammerheads and bull sharks down here."

Heuter said the Massachusetts project, set to begin on Sept. 4, is similar to the work done in South Africa. "We'll be tagging, measuring and taking samples," he said.

The sharks are generally caught from a small boat, using tuna for bait and a quarter-inch braided line with several buoys attached to wear down its resistance. They are then led into the platform, which is submerged alongside the mother ship.

Working on the body of a 4,000-pound great white is not as terrifying as it sounds, Whitworth said. "If you lay them on their side they go into a state of immobility," he said. "When we roll them over they wake up just fine."

Researchers also take parasites and cultures from a captured shark's mouth, anal duct and gills, he said.

"A lot of damage, post-bite, results from infection," Whitworth said. "So scientists are trying to learn more about the bacteria in a shark's mouth."

The sharks remain out of the water for between seven to 15 minutes on average and a hose provides a flow of water over their gills while they are on the platform, he said.

For Whitworth, who has chased white sharks anywhere they can be found, coming to Cape Cod is a new experience.

"But there are two places in the world right now where you are guaranteed to find great whites, South Africa and Chatham," he said.